SCILIVSY 12 Chapter Notes - Chapter 4: Sexual Selection, Natural Selection
19 Jun 2018
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If#breeders#can#select#characteristics#in#their#domestic#populations,#
can#nature#act#the#same#way?#Darwin#thinks#yes
§
Breeders#selecting#desired#characteristics# for#animals
○
While#breeders#can#select#variations#that#are#beneficial#for#them,#
omniscient#nature#has#the#power#to#develop#and#select#variations#that#are#
imperceptible#to#man#and#beneficial#to#species#in#ways#that#man#might#
never#have#considered
○
Since#advantageous#variations#are#heritable,#they#can#be#perpetuated#in#
future#generations
○
Wolf#with#slimmer#features#can#run#faster#to#escape#predators
§
A#plant#that#contains#a#sweet#nectar#or#colorful#petals#may#attract#
more#insects#than#other#plans#which#will#spread#that#plants#pollen
§
Examples:
○
Natural#selection:
•
Another#factor#in#species#evolution
○
these#variations#will#be#passed#onto#offspring
§
Male#individuals#with#variations#that#allow#them#to#successfully#attract#
females#are#more#likely#to#reproduce#and#therefore#to#produce#more#
offspring#than#others
○
These#variations#may#not#directly#impact#the#ability#of#
an#individual#organism#to#survive#in#nature,#but#its#
variations'#utility#allows#these#variations#to#be#selected#
and#perpetuated#in#a#species
®
If#any#variation#in#these#characteristics#were#to#give#male#
birds#a#better#chance#of#mating,#that#variation#would#likely#
spread#to#the#birds'#offspring#and,#as#a#result,#would#become#
predominant#in#the#population#in#subsequent#generations
□
Male#birds#singing#to#potential#mates,#displaying#various#brightly#
colored#feathers,#performing#antics#to#attract#attention
§
Examples:
○
Sexual#selection
•
Allows#certain#organisms#to#survive#in#that#particular#environment#
out#disadvantageous#ones
§
Explains#why#floral#and#animal#life#is#unique#in#island#environments
§
Isolation#is#key#to#natural#selection#as#it#creates#a#situation#in#which#few#
individuals#live#in#a#specific#area#in#which#no#new#organisms#will#be#
introduced
○
Large#geographical#areas#(no#isolation)#allow#species#to#spread#and#
propagate#widely,#increasing#species#numbers#and#overall#chances#of#
survival#in#a#range#of#environments
○
Geographical#requirements
•
Particular#variations#are#selected#over#others,#these#variations#lead#to#a#
divergence#in#characteristics#fro#the#parent#species
○
"Branches"#are#created#and#some#branches#end#as#species#become#
extinct,#while#other#branches#multiply#as#more#subspecies#develop#and#a#
new#species#becomes#a#parents#species
○
Natural#selection#to#divergences#of#character#and#creation#of#new#species•
Question#4:
The#figure#introduced#in#this#chapter#illustrates#how#adaptations#and#the#divergence#
from#certain#species-specific#traits#create#"branches"#among#a#common#species.#As#
each#branch#has#characteristics#unique#to#that#branch,#some#branches#can#ultimately#
become#extinct#while#other#branches#with#advantageous#variations#may#develop#and#
increase#its#population.#The#struggle#for#existence#that#Darwin#discusses#is#partially#
due#to#the#fact#that#organisms#with#certain#variations#are#better#suited#for#existence#
than#others.#
Chapter(4
Tuesday,# September# 20,#2016
1:31#PM
